I have seen a couple of articles about how to integrate external libraries to debug our PHP code (i.e. firePHP) but after you read this article you will realize that there is no need for such libraries when using Yii.

Yii comes with a set of powerful classes for logging. If you have read the documentation about logging messages, you have noticed that we can actually decide which messages we wish to log. And this is exactly what we are going to do, using CWebLogRoute to create a Yii version of firePHP.

'log'=>array('class'=>'CLogRouter',
'routes'=>array(array('class'=>'CWebLogRoute',
//// I include *trace* for the // sake of the example, you can include// more levels separated by commas'levels'=>'trace',
//// I include *vardump* but you// can include more separated by commas'categories'=>'vardump',
//// This is self-explanatory right?'showInFireBug'=>true),

But the above code is too long to write, lets use Qiang's suggestion. We are going to write a function in our index.php page exactly as that of firePHP:

//// In your index.php or your globals.php filefunctionfb($what){echoYii::trace(CVarDumper::dumpAsString($what),'vardump');
}//// using the above examples now we could$test = 'This is a test';
fb($test);

And that's it; our nice Yii PHP variable debugger and the best of all, no external libraries included.

I thinks it is not great, and use var_dump directly in view is better.
And so, this is not support of ajax request.
Also, I thinks use Integrating FirePHP is great. here:
http://www.yiiframework.com/wiki/84/integrating-firephp

logging to firebug etc is fine ... and I was enjoying logging all db calls to firebug, and being able to diagnose how Yii was using the db directly into FireBug ... but it destroys AJAX and similar functionality, so half my pages flaked .. which sort of makes its usefulness as a debug tool limited .. if someone could figure out how to have it turned off for AJAX mode .. that would help.

I got depressed recently when my firephp extension stopped working with latest firefox/firebug.This is a nice solution I was unaware off,just tried it and works perfectly.
What I miss though,I'd like to see the name of the variable in my console(besides the value),and I cant find a way to do it.The second argument of trace will not accept any string...

Hi Trej, thanks for commenting... I used to that also, but if you try to compare the way var_dump works and the way dumpAsString does render the variables, you will see the difference between both approaches.

Also, for a guy like me that uses extensively AJAX, var_dump is a very bad option and to develop a script that writes to console without interfering normal AJAX calls isn't as easy as it seems, as I used to normally had to encode within the success, failure, complete... and so on, js functions.

Again, all options are depending on the way a programmer feels comfortable with.